With the continued anticipation of higher speed requirements in the computer hard drive industry, a transition from Parallel Advanced Technology Attachment (PATA) interfaces to Serial Advanced Technology Attachment (SATA) interfaces is currently underway. See, e.g., J. Donovan, “Here Comes Serial ATA,” E. E. Times, April 2003; and L. Wood, “SATA: Evolutionary or Revolutionary Disk Technology,” EnterpriseStorageForum.com, March 2003. SATA meets the rising hard drive performance requirements without significant increases in price. Further, SATA improves airflow and cuts power consumption by replacing PATA ribbon cables with low voltage serial cables. A SATA interface is typically integrated in a System-on-Chip (SOC) configuration. Such SOCs are frequently utilized in desktop computers. Due to extreme cost pressure in the industry, package solutions for SOCs that offer the right level of performance, while having the lowest cost, will be sought for use in the higher speed systems. Thus, the increased performance demands of the systems have not stopped production and use of traditional leadframe-based packaging. Recent innovations have allowed the more traditional package structures to reach into the markets of the more demanding applications. See, e.g., S. Jewler, “Current Challenges Dictated by Today's IC Packaging Trends,” Solid State Technology, April 2003.
A standard SOC is a Thin Quad Flat Package (TQFP) which provides a space efficient packaging solution, resulting in smaller PWB space requirements. The TQFP includes a central die upon which an integrated circuit device is disposed. The central die is electrically connected to a plurality of leads that extend outward from the die and beyond the packaging, or the material which encapsulates the die and the leads. The ends of the leads may then be soldered to traces on a PWB. The reduced height and body dimensions of the TQFP are ideal for space-constrained applications, such as laptop PCs, video/audio devices, data acquisition devices, office equipment, disc drives, and communication boards.
A preferred SOC package is the Exposed Pad Thin Quad Flat Package (ETQFP). A more particular example of such a package is the ExposedPad L/TQFP commercially available from Amkor Technology of West Chester, Pa., U.S.A. In this type of package, the integrated circuit die is shifted downward and an associated die pad is exposed on the underside of the package. The exposed die pad significantly increases the thermal efficiency of the package. The ETQFP can increase heat dissipation by as much as 110% over a standard TQFP, thereby expanding operating parameter margins. Additionally, the exposed pad can be connected to ground, thereby reducing loop inductance for high-frequency applications. The exposed pad is soldered directly to the PWB to realize the thermal and electrical benefits.
An additional product also available from Amkor Technology is the MicroLeadFrame, which replaces all the traditional leadframe leads on the perimeter of the integrated circuit package with lands on an underside of the package. The lands are used to provide electrical connection of the integrated circuit package to the PWB. This modification allows package size to be reduced, while also reducing lead inductance for high-frequency applications. This technology also incorporates the exposed pad on the bottom surface of the package to provide an efficient heat path.
The adaptation of these packages is intended to extend the useful life of the low-cost TQFP, so that it may comply with anticipated higher speed requirements of the systems, while remaining inexpensive. However, a problem exists in that users generally prefer a circuit board arrangement having high-speed lines that may be routed to an integrated circuit on a top surface of a PWB, while maintaining the traditional properties of TQFPs, such as leadframe leads. Conventional TQFPs, including the above-noted ETQFP, typically do not include high-speed leads, and instead have leadframe leads with a tight pitch preventing trace access to the underside of the packaged integrated circuit from the top surface of the PWB. The MicroLeadFrame is smaller in size than traditional TQFPs and does not provide leadframe leads. Thus, a need exists for an improved package that addresses the drawbacks of the conventional arrangements.